1,721,000 research outputs found
Introduzione al Calcolo delle Probabilità
No full textIl libro presenta una introduzione al calcolo delle probabilità con particolare attenzione all'apparato definitorio
Which company would you like to fly with?
No full textAbbiamo posto ad ascoltatori ingenui – vale a dire né studenti o docenti, né gente più o meno del mestiere – il quesito che qui riproporremo. Diciamo subito che quel nostro interrogare non era una ricerca sul campo per contribuire alla discussione se una teoria dell’inferenza statistica o delle decisioni in condizioni di incertezza debba essere anche descrittiva oltreché normativa. Volevamo soltanto appagare la nostra curiosità eccitata dalla lettura di alcuni dei contributi raccolti nell’interessante libro curato da Kahneman et al. (1982), in particolare quello di Kahneman e Tversky a p. 48 sgg. Del resto – come si vedrà – il nostro quesito era in effetti volutamente mal posto – descrivevamo incompletamente lo scenario – cosicché dall’interrogato c’era da attendersi non la scelta di una decisione, ma piuttosto un “non so” o meglio un “dipende”. Se qui la riproponiamo è perché ci sembra un modo didatticamente efficace per presentare l’essenziale della teoria classica delle decisioni in condizioni di incertezza (Di Bacco (1992)). E diciamo, “classica” perché – oggi come oggi – non solo si giudica “ottima” una decisione se e solo se essa è coerente con quella teoria, ma anche perché i ben notiarnesi dell’inferenza statistica – la “stima” e il “test” – sono detti “ottimi” se possono essere interpretati come decisioni “ottime” Piccinato (1996)
An alternative Approach to Expected Utility Theory
No full textIt is well known that in the Expected Utility Theory, a Bayesian decision maker is indifferent to a costless information, if that does not change the optimal decision. In this paper it is proved that, if indifference with respect to a non-significant information is assumed, (under a very natural stability hypothesis) a Bayesian agent should follow the expected utility theory; this provides a system of axioms for the theory of expected utility, which is alternative to the classical one
Aggregazioni di Probabilità
No full textWe develop a new outlook on the use of experts' probabilities for inference, distinguishing the information content available to them from their probability assertions based on that information. It allows a statistician to specify a flexible function that represents a posterior probability of interest conditioned on all the information available to any of the experts. We work here in the restricted case of one expert, but the results are extendible in a variety of ways. The combining function is computed from statistics provided by the expert personal probability assertions which are based on the data. Considered as functions of the data through the individual expert assessing functions, they thus provide a statistic. Given some assumptions this assertion is shown to be sufficient for the direct computation of thedesired posterior probability. We develop a mixture distribution structure that allows integration in one dimension to yield the complete computation
Recent changes in temperature extremes across the north-eastern region of Italy and their relationship with large-scale circulation
No full textThe present study is an analysis of recent changes (1981-2016) in air temperature across the north-eastern region of Italy (NERI), located in a transition zone influenced by the Mediterranean and continental climatological regimes. Annual and seasonal trends in mean maximum and minimum temperatures as well as in selected extreme indices are investigated using high-quality and homogenised daily data deriving from a distributed network of 50 weather stations. The results reveal an overall widespread warming, particularly intense in spring and summer, with significant positive trends in mean and daytime (maximum-related) temperature extremes, especially at lower altitudes. No substantial elevation dependency is observed for trends in minimum-related temperature indices, which are generally characterised by lower spatial variability. Comparable positive and negative trends are identified in the frequency and duration of warm- and cold-related extremes indices. Finally, the influence on temperature extremes of dominant large-scale circulation modes in southern Europe (North Atlantic Oscillation [NAO] and East-Atlantic [EA] pattern) is examined. The results indicate that especially NAO-induced changes can explain observed temperature trends over the NERI, while the impact of the EA pattern is slightly weaker
analisi predittiva bayesiana di un indicatore di qualità in un processo chimico-industriale.
No full textDa alcuni anni CIBA SC. effettua, nel suo stabilimento di Pontecchio Marconi in Bologna, il monitoraggio elettronico di alcune proprie linee di produzione. Nel presente lavoro – prosecuzione di precedenti collaborazioni (si veda Catellani e Frederic(2001) )– viene analizzato, da un punto di vista statistico, il processo di produzione di un intermedio prodotto da CIBA. Una volta analizzati i dati disponibili con tecniche esplorative viene implementato un modello additivo eteroschedastico di impostazione Bayesiana predittiva. Tale modello mette in evidenza interessanti relazioni tra alcune variabili presenti nel sistema e un indicatore di qualità del prodotto finito
On the experimental assessment of De Marchi’s discharge coefficient for inclined side weirs: transfer functions for the application of alternative methods
No full textThe use of De Marchi’s approach, solving the 1D dynamic equation of spatially varied steady flow with non-uniform discharge, is commonly accepted in the design of side weirs. A key issue in applying De Marchi’s formula is the assessment of the discharge coefficient CM. However, no explicit equation for the experimental determination of CM can be derived for inclined side weirs, due to the longitudinal change of crest’s height. In this context, the present study analyzes the feasibility of using alternative methods for the estimation of the discharge coefficient (i.e. Dominguez’s, Schimdt’s or other approaches), which may be suitable to be used in De Marchi’s equation also for inclined side weirs. However, this solution necessarily yields an additional error in the estimation of CM, due to the different modelling assumptions underlying these other methods. Therefore, in this study, the magnitude of this error is first quantified using a 1D numerical model for different tested hydraulic conditions and geometric configurations of the side weir, including: Froude number (only subcritical flows), channel and friction slope, crest angle, water depth/weir height and weir length/channel width ratios. Results indicate that error factors (i.e. observed/predicted ratio) in the assessment of De Marchi’s coefficient can range from 0.57 to 15.60 for inclined lateral weirs, depending on the selected modelling approach. As a second step, a Multilayer Perceptron Neural network is applied to derive transfer functions from the discharge coefficients calculated using the different methods to the corresponding values of CM to be used in De Marchi’s weir equation
Probability of Mitochondrial Lineage Extinction in Female Offspring, Modern and Paleolithic: Branching Process Analysis
No full textWe evaluate the probability of extinction of the female offspring of two populations of women: the one Paleolithic, the other that of Italy today. In both cases it is assumed that possible extinction arises exclusively on account of limitations in the degree of fertility and/or an imbalance in the sex-ratio of the population. The value is obtained as the probability that a Branching Process describing the evolution of the offspring by a progenitor degenerates to a “Blank Generation,” that is, a generation without women. Mathematically, it derives from a solution between 0 and 1 of a linear equation whose coefficients are the probabilities that a single progenitor breeds various integer numbers of daughters. We evaluated such probabilities by consulting literature. The probability of branch extinction is also the probability of extinction of progenitor’s mitochondrial lineage
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